It has recently become known that a main cause of plane crashes due to technical problems in the aircraft is merely the breakdown of insulation of electrical wirings. Moreover, demand for the systems such as control systems for nuclear power plants, spaceships, submarines, or industrial control equipment, which require high stability in an electrical wiring, are is increasing, the diagnosis and evaluation of the reliability of the electrical wiring are becoming important activities.
In addition, precise diagnosis to determine whether there is an abnormality in a conducting wire and to determine the location thereof are important technical issues at a site for producing various kinds of wires in order to evaluate the quality and consistency of the produced wires.
Accordingly, so far, such a precise diagnosing and location measuring technique, namely, an electrical wiring diagnosis system, mainly adopts reflectometry to diagnose whether there is an abnormality in a wire by transmitting a certain signal to the wire and then measuring the reflected signal.
Reflectometry is performed only in the time domain or in the frequency domain. In reflectometry, a certain application signal is transmitted to the wire, a reflected signal, which has been reflected and returned, is measured, and then whether there is a fault, such as an open circuit, a short circuit, or a discontinuity, is determined, as well as the fault location or characteristic impedance of the wire. There are various kinds of reflectometry, including time-domain reflectometry, standing-wave reflectometry, and frequency-domain reflectometry.
However, in diagnosing a fault location and type of cable by analyzing the reflected signal for such an application signal in the time or frequency domain, restrictions have occurred which include the case where the application signal and the reflected signal overlap each other due to the proximity of a fault location to an application location, the case where the intensity of the reflected signal is weak, thus causing a distance measurement error due to the remoteness of the fault location from the application location, or the case where the accuracy of coupling distance measurement is lowered to cause degradation in the accuracy and reliability of cable diagnosis results.
Accordingly, the present invention proposes a measure for detecting a fault type and a fault location of a cable to be diagnosed on the basis of a correction signal, from which an application signal is removed, and a reflected signal.